DE102008015949A1 - Test method and device for a manipulator brake - Google Patents

Abstract

A method according to the invention for testing a brake of a manipulator, in particular of a robot (1), comprises the steps of: applying a predetermined driving force (tauA) to the manipulator (S10); Closing the brake (S20); Detecting the movement (q; dq / dt; d2q / dt2) of the manipulator (S30) and evaluating the brake based on the detected movement (S40).

Description

The The present invention relates to a method and an apparatus for testing a brake of a manipulator, in particular a robot.

The axes of movement of manipulators, in particular industrial, lightweight or Telerobotern, are braked during operation generally by the drives, which apply appropriate braking forces against the direction of movement. Brakes are mainly used as parking brakes to secure the pose of the stationary manipulator. However, for example, for a quick emergency stop the brakes can also in addition to the drives or, for example, at a stop 0 according to EN 60204 , be closed in place of the drives to decelerate the still moving manipulator. In particular, for such applications, it is necessary to ensure the function of the brakes.

The EP 1 239 354 B1 proposes a method for testing a manipulator brake, according to which a stationary axle is acted upon when the brake is closed with a predetermined drive torque. If the axis moves despite the brake being closed before reaching or exceeding the specified drive torque, then the brake is rated as not functional.

Due to the different values of coefficients of adhesion and sliding friction, brakes can regularly apply holding forces at standstill, which are higher than the braking forces decelerating during operation during operation. If the maximum static friction force of a brake is exceeded, the manipulator starts to move, whereby the still closed brake opposes this movement with a lower braking torque. In particular, in order to assess the function of a brake as a service brake, so to slow down a movement, therefore, the method of EP 1 239 354 B1 little suitable. This becomes particularly clear for speed-dependent brakes such as eddy-current brakes, which do not provide significant braking torque at standstill.

The EP 1 215 475 B1 therefore proposes a method for testing a brake, after which the motor current of a variable-speed electric motor is detected after the brake has been closed. Since here the speed-controlled electric motor, the axis - while applying a correspondingly larger drive torque - continues to move, in contrast to the aforementioned EP 1 239 354 B1 Advantageously detects the operating torque of the brake, which provides them for braking a movement - it just corresponds to the drive motor to be additionally supplied by the electric motor after closing the drive torque to maintain the target speed.

adversely In this test, the brakes are being dragged by the electric motor is rotated, as well as the electric motor, the closed Overcome the brake and maintain a specified setpoint speed must, heavily loaded. In addition, this test method is on adapted previous robot controls, which formed usually position-controlled are and on the specification of a desired position or - speed based. Increasingly, however, in manipulators, in particular in robots, model-based regulations, such as force regulations used in which target drive forces are specified.

task The object of the present invention is to test a brake to improve a manipulator.

These The object is achieved by a method having the features of the claim 1 solved. Claim 12 provides a device claim 13 and 14 a computer program or a computer program product for Implementation of a method according to claim 1 under protection. The subclaims relate to advantageous developments.

One Inventive method is used for testing one or more, in particular all brakes of a manipulator, especially a robot such as an industrial, Lightweight or Teleroboters. The brake to be tested can in particular mechanically, for example as disc, drum, Wedge or shoe brake, or electrodynamically, for example as Eddy current or multi-disc brake or brake generator act. she may preferably be electrical, electromagnetic, electromotive, hydraulically and / or pneumatically actuated by a brake control, in a preferred embodiment as well as a tester for carrying out a method according to the invention Method implemented in a robot controller or as a separate Device can be provided. The term "control" as used herein expressly a regulation.

To the inventive method is a predetermined Driving force applied to the manipulator. To the more uniform Representation becomes an opposing force pair, i. e. a torque, hereinafter also referred to as a force, so that, for example, a drive or braking force alike denotes a drive or brake torque and force sensors also include torque sensors.

The application of a predetermined driving force comprises in particular the specification of a temporal and / or state-dependent Ver Running of the driving force, for example, an at least piecewise constant, especially vanishing driving force, with a time linear, square or according to another predetermined function larger or smaller driving force, or a driving force of state variables of the manipulator, in particular one or more axis positions and / or speeds depends. Such driving forces can advantageously be applied by force-controlled drives, in particular force-controlled electric motors. It can be reduced by suitable specification of the driving force advantageously a load of the brake and the drive during the test.

While the predetermined driving force is applied to the manipulator, the brake to be tested is closed. Thus, the Function of the brake as a service brake, i. e. to slow down one Movement to be checked. The brake is preferred completely closed, such as a voltage, which releases an electromagnetically actuated brake Zero is lowered. However, it is equally possible the brake targeted incomplete, for example, to a to close the predetermined percentage of a maximum state, to check the braking effect of this condition. For this purpose, for example, the venting tension on a lower value so that the brake partially, but not yet completely closed. Prefers can in this regard also several positions of Brake are tested, about a braking performance at a to 25%, 50%, 75% and 100% closed brake, with 0% a fully released brake and 100% one not ventilated brake corresponds.

there and / or subsequently a movement of the manipulator detected. This can be, for example, the recording of the time course the position of the manipulator, so the position or position of a or more, especially all axes of the robot, but also the location and / or orientation of a reference coordinate system of the manipulator, for example its Tool Center Point (TCP) include.

For this For example, the axle or joint angle through Angle encoder or the like detected and, if necessary, by means of Forward kinematics in Cartesian coordinates, Denavit-Hartenberg parameters or the like.

Out the position can, preferably by single or multiple numerical Differentiation, the speed or acceleration of the manipulator be determined. Similarly, the speed also detected for example by tachogenerators or the like become. The acceleration can, for example, by numerical Differentiation gained or by acceleration sensors or such in turn are detected. Basically even higher time derivatives, such as a jerk of the manipulator as a time derivation of its acceleration conceivable so that in general the movement of the manipulator its position, Speed, acceleration and / or even higher time derivatives, each in the coordinate space of the joint or axle positions and / or may include in the Cartesian workspace of the manipulator.

bestimmen, wobei M die generalisierte Massenmatrix, dⁿq/dtⁿ die n-te Zeitableitung der generalisierten Koordinaten, beispielsweise der Gelenkpositionen, und h den Vektor der übrigen generalisierten Kräfte bezeichnet. Die von der zu prüfenden Bremse aufgebrachte Bremskraft beeinflusst daher die Beschleunigung und entsprechend insgesamt die Bewegung des Manipulators. Bringt beispielsweise eine vollständig geschlossene Bremse eine sehr hohe Betriebsbremskraft auf, so erfährt der Manipulator eine entsprechende hohe negative Beschleunigung.Based on this detected movement, the brake is now evaluated according to the invention. Because the (at least partially) closed brake exerts a braking force T _B on the manipulator, which together with the other forces acting on it, in particular the (predetermined) driving force T _A , the weight, a frictional force, gyroscopic forces such as centrifugal and Coriolis and the like, the movement of the manipulator according to

where M denotes the generalized mass matrix, d ⁿ q / dt ⁿ the n-th time derivative of the generalized coordinates, for example, the joint positions, and h the vector of the remaining generalized forces. The braking force applied by the brake to be tested therefore influences the acceleration and accordingly the movement of the manipulator. If, for example, a completely closed brake applies a very high service brake force, then the manipulator experiences a correspondingly high negative acceleration.

to Evaluation of the brake based on the detected movement is therefore in an embodiment of the present invention, a Movement descriptive size, especially the Position, speed and / or acceleration of the manipulator compared with an allowable limit. For example the negative acceleration achieved by the brake a minimum delay to be achieved by the brake during operation, the brake is rated as functional. additionally or alternatively, the rating may also be based on speed by detecting, for example, whether a braked movement despite accelerating forces due to drive, gravitation or the like does not exceed an allowable speed.

Additionally or alternatively, in another embodiment of the present invention, one of the brake is based on the sensed motion the manipulator applied braking force determined and compared with an allowable limit. In particular, when the other forces acting on the manipulator are known, as is the case for example with the given driving force or the position-dependent weight force, or may be neglected, as may be assumed, for example, for bearing friction, air resistance and the like According to equation (1), the braking force τ _{B determined} from the detected movement and checked whether this braking force reaches or exceeds an at least to be reached by the brake during braking.

Of the aforementioned limit for movement, in particular Acceleration or braking force can be multiplied by a safety factor Setpoint for the brake correspond. Should For example, a brake an axis of the manipulator at maximum speed can shut down within a given time the limit by dividing this given time by a Safety factor greater than one can be obtained.

In a preferred embodiment of the present invention can be the size describing the movement and / or the braking force determined based on the detected movement also thereby be compared with the limit that a quotient with this Limit is formed, thus the quality of the brake in relation to the then serving as a reference value limit, for example in percent, indicates. So can advantageously a brake, for example 150% of the required minimum delay achieved and thus having large safety reserves, of a brake which are 100% of the required minimum delay achieved, so only just as functional to evaluate is. In this way, especially safety reserves the brake are detected. In this preferred embodiment Therefore, the brake is not only binary in "functional" or "not functional "but their goodness finer rated, for example, in "not functional", "straight still functional "," functional with small safety reserve "," functional with a large safety margin "and the like, where individual ranges of the quotient are different grades assigned or the quotient as such, the quality of the brake Are defined.

To Alternatively, the movement can be descriptive of this purpose Size and / or based on the detected movement certain braking force also compared with different limits and so classified by, for example, the limit values successively get bigger or smaller and for example a brake whose braking power is also a second, larger Exceeds the limit, is rated better than a brake, whose braking force exceeds only a first, smaller limit, but not the second, bigger one.

The force applied to the manipulator driving force can be specified such that the manipulator changes its direction of movement and / or movement speed. In particular, when rotating about an axis deviating from the vertical axis, the weight acts in one direction of braking, accelerating in the other. If the driving force is predetermined in such a way that the manipulator passes through both directions of movement, thereby closing the brake and detecting the movement of the manipulator, the effects of gravity can be compensated. For example, if a limb of a manipulator in a first movement q1 (t) is pivoted upwards about the horizontal, so that the weight force causes a restoring force -τ _G , and then pivoted in an opposite movement q2 (t) to the horizontal downwards, so that an accelerating force τ _G results from the weight force, the acting weight force can be eliminated from equation (1) and thus the actually acting braking force τ _B can be determined.

ergibt, mit der Beschleunigung d²q²/dt² verglichen, die sich beim Bergabziehen mit dieser Kraft ergibt

This can be illustrated by a very simple example. Let the sliding friction τ _B = μ × m × g × cos (α) of a pad, which is moved by the constant force F on an inclined plane inclined at α, be evaluated, where m is its mass, g is the gravitational constant and μ denotes the sliding friction coefficient, then its acceleration d ² q1 / dt ² in the direction of the inclined plane when climbing with F, resulting from

gives, compared with the acceleration d ² q ² / dt ² , which results when pulling down with this force

By subtracting both detected movements resulting in known tensile force F and detected acceleration d ² q / dt ^2, the effective sliding friction or braking force

A change in the speed of movement allows the assessment of the brake as a service brake for different speed ranges. For example, since the coefficient of sliding friction of a friction brake as well as the induced resistance The torque of an eddy current brake are speed-dependent, so the suitability of the brake can be checked as a service brake for different speeds of the manipulator. Likewise, the method according to the invention can also be carried out in succession with drive forces of different magnitudes, which lead to movements of the manipulator that are of different speeds.

The Actually, the driving force applied to the manipulator can be substantially reduced a test force of the brake, in particular one with a Safety factor multiplied minimum operating force of the brake correspond. For example, an arm of a manipulator to the Vertical with 1.3 times the prescribed braking torque pivoted and the brake acting on this axis closed, so the arm must respond to it with a corresponding deceleration. Depending on whether and if necessary by how many times this deceleration corresponds to a prescribed minimum delay is then the brake rated.

The Brake can in a preferred embodiment one or more times closed and then reopened, while the movement of the manipulator is detected. This will on the one hand, the above-described reversal of the direction of movement facilitates, on the other hand, so-called brake fading, in particular the Decreasing the braking effect with the number of braking evaluated become.

The inventive method can be specified in Time intervals are repeated, with the won Brake ratings, in particular together with state parameters during the evaluation, can be saved. Such state parameters can be position, for example and / or speed of the manipulator, temperature, gripped Payload, time of evaluation and the like include. Consequently the history of the reviews can be logged. In a preferred development can be based on this evaluation protocol, for example, by suitable, in particular linear or exponential Extrapolation of reviews over time, even one Forecast for the brake to be created. Sinks, for example the above described with reference to a reference value quality of the brake over equidistant Ratings from 150% over 140%, 130%, 120% to 110%., So can be predicted that this brake at the time of the next Measurement will just be functional, then no more. This can prematurely wear the brake detected and prevented and failure.

Several Braking the manipulator can according to the methods described above, successively or simultaneously be closed while given drive forces applied to the manipulator and its movements are detected. Closing at the same time can save time Checking the brakes acting on different axles become. By checking individual axes one after the other On the other hand, in particular, a mutual influence of the test results be avoided.

Further Advantages and features emerge from the subclaims and the embodiments. This shows, partially schematically:

1 a robot with a test apparatus according to an embodiment of the present invention;

2 : the position of an arm of the robot according to 1 during the process according to 3 ; and

3 Fig. 1 shows the flow of a brake testing method according to an embodiment of the present invention.

1 shows a bipartite robot 1 with a rotatable around the vertical hull, a rotatable about the horizontal arm and one in the controller, not shown 2 of the robot 1 Implemented test apparatus according to an embodiment of the present invention for carrying out the following in more detail with reference to the 3 described method. The joint angle q of the arm against the vertical describes in sufficient detail for the following explanations the position of the robot 1 ,

wobei m die Masse des Armes und l seine Schwerpunktlage beschreibt. In einem ersten Schritt S10 (vgl. 3) wird durch einen Antrieb der Horizontalachse (nicht dargestellt) ein über der Zeit t vorgegebenes Antriebsdrehmomentes τ_A auf den Arm aufgebracht, das zunächst bis zum Zeitpunkt T linear zunimmt (vgl. (1')) und ab t = T dem Gewichtskraftdrehmoment mgl des horizontal ausgestreckten Armes entspricht, wie in 2 punktiert dargestellt.With respect to this position, according to (1), the movement of the robot arm is neglected by other influences

where m is the mass of the arm and l is its center of gravity. In a first step S10 (cf. 3 ) is applied by a drive of the horizontal axis (not shown) over the time t predetermined drive torque τ _A on the arm, which initially increases linearly until time T (see (1 ')) and from t = T the weight torque mgl of horizontally outstretched arm corresponds, as in 2 shown dotted.

Without brakes (τ _B (t) = 0) the arm would be simplified in the in 2 Swinging up in a chain-dotted manner: first of all the arm starts - delayed due to its inertia - the to follow increasing drive torque. From about 45 °, the restoring weight force torque exceeds the drive torque and slows down the movement. At the end of the movement, the drive and weight torque keep their balance, so that the arm no longer experiences acceleration, but is in equilibrium with forces and moments.

According to a brake test method according to an embodiment of the present invention, the operation of which is described in 3 is sketched, the brake acting on the axis of rotation of the arm brake (not shown) is closed in a step S20 at time tb. This is formed in the embodiment as a mechanical, electromagnetically released jaw brake, the jaws act on the rotor of the drive designed as an electric motor arm axis and exert a direction of movement opposite service brake torque τ _B on this. This is slightly speed-dependent in the rotating rotor, but can be considered simplified as a constant and is in any case due to the comparison with the coefficient of static friction μ ₀ smaller sliding friction coefficient μ between the jaw and rotor less than a maximum aufbringbares by the brake holding torque.

Accordingly, as in 2 shown in solid, from the time tb, the arm increasingly slower, since the decreasing drive torque τ _A now counteract both the increasing weight torque and the braking torque τ _B. Therefore, the arm comes to a standstill at time ts1 without reaching the horizontally extended position (FIG. 2 ).

If the brake exerts, for example due to wear, only a smaller braking torque τ _B on the horizontal axis of the robot during the same test procedure 1 out, so the arm comes to a later time ts2 and in a higher position to a standstill, as in 2 dashed lines is drawn. Both the time ts to standstill and the thereby achieved position q (ts) thus represent, as well as, for example, the occurring delay d ² q / dt ² a measure of the quality of the brake, in particular its function as a service brake in step S30, the joint angle q (t) of the arm is recorded and in a step S40 the brake is evaluated on the basis of this detected movement.

For this purpose, for example, a minimum time to be reached during this test is divided by the time ts0 reached until standstill ts0. This quotient ts0 / ts represents a proportional measure for the quality of the brake, with a quotient ts0 / ts <1 of a non-functional brake, a quotient ts0 / ts1 of a just functional brake, the quotient ts0 / ts2 = 120% (dashed line in 2 ) of a functional brake with a small safety margin and the quotient ts0 / ts1 = 150% (solid in 2 ) corresponds to a functional brake with a large safety reserve.

This rating is recorded along with the temperature and time of the test and the test is repeated at predetermined time intervals. For example, lie between the in 2 solid or dashed tests shown 200. Days of normal operation of the robot 1 , it can be extrapolated that the brake will not be functional after another 300 days of normal operation.

1

robot

q

position (Joint angle)

τ _A

drive torque

τ _B

Service brake torque

t

Time

tb

Shut down the brake

ts1, ts2

Time until standstill

T

time constant drive torque

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - EP 1239354 B1 [0003, 0004, 0005]
• - EP 1215475 B1 [0005]

Cited non-patent literature

• - EN 60204 [0002]

Claims (14)

Method for testing a brake of a manipulator, in particular a robot ( 1 ), comprising the steps of: - applying a predetermined driving force (τ _A ) to the manipulator (S10); - closing the brake (S20); Detecting the movement (q; dq / dt; d ² q / dt ² ) of the manipulator (S30); and - evaluating the brake based on the detected movement (S40). Method according to claim 1, characterized in that the drive force applied to the manipulator is predetermined in this way is that the manipulator his direction of movement and / or movement speed during the exam changes Method according to one of the preceding claims, characterized in that the applied to the manipulator Driving force essentially a test force of the brake, in particular a multiplied by a safety factor minimum operating force corresponds to the brake. Method according to one of the preceding claims, characterized in that the brake one or more times closed and then reopened while the movement of the manipulator is detected. Method according to one of the preceding claims, characterized in that, while the predetermined driving force is applied to the manipulator, the brake completely or incomplete, in particular substantially to 25%, 50%, 75% and / or 100%, with 0% being a complete one ventilated brake and 100% non-ventilated Brake corresponds. Method according to one of the preceding claims, characterized in that for detecting the movement of the manipulator whose position (q), speed (dq / dt) and / or acceleration (d ² q / dt ² ) is detected. Method according to one of the preceding claims, characterized in that the brake based on the detected Movement is assessed by a variable describing the movement, in particular the position, speed and / or acceleration of the manipulator is compared with a limit value. Method according to one of the preceding claims, characterized in that on the basis of the detected movement, a braking force applied to the manipulator by the brake (τ _B ) is determined and compared with a limit value. Method according to one of the preceding claims 7 to 8, characterized in that the limit one with a Safety factor multiplied target size for the brake or a reference value. Method according to one of the preceding claims, characterized in that it at predetermined intervals is repeated, and the resulting assessments of the brake, especially together with state parameters during the Rating, saved. Method according to one of the preceding claims, characterized in that a plurality of brakes of the manipulator are closed successively or simultaneously, while predetermined driving forces (τ _A ) applied to the manipulator and its movements are detected. Testing device for a manipulator, in particular a robot ( 1 ), comprising: a drive controller for applying a predetermined driving force (τ _A ) to the manipulator; a brake control; detecting means for detecting the movement (q; dq / dt; d ² q / dt ² ) of the manipulator; characterized in that the test device is set up for carrying out a method according to one of the preceding claims. Computer program that a procedure after a of claims 1 to 11 executes when in a Test device according to claim 12 expires. Computer program product with program code based on a machine-readable carrier is stored and a Computer program according to claim 13.